In the movement guide device of this kind, when dust and foreign substances enter the gap between the track rail and the mobile block, the entry of dust and foreign substances causes the abnormal abrasion of the rolling elements and a rolling surface for these rolling elements, which in turn decreases the life of the device. Thus, dust-proof means is required to prevent the entry of dust and foreign substances through such a gap.
Conventionally, a seal member made of urethane rubber or the like is well known as such dust-proof means. The seal member is mounted on both sides of the mobile block in a moving direction and a tip of a lip portion provided on the seal member is brought into close contact with a surface of the track rail. The seal member is configured so that the lip portion removes dust and foreign substances deposited on the track rail as the mobile block moves, to thereby prevent those foreign substances from entering inside of the mobile block.
Conversely, there is a problem that the seal member molded from urethane rubber generates a large frictional force between the lip portion and the track rail, and hence in terms of ensuring smooth movement of the mobile block relative to the track rail, it is difficult to set extremely large pressure contact force of the lip portion relative to the track rail.
For this reason, as a structure suitable for a movement guide device for use in an environment in which many foreign substances are deposited on the track rail, a structure in which a plurality of the seal members are mounted on the mobile block in an overlapping state is also suggested (JP 09-42284 A).
On the other hand, JP 11-294451 A discloses a seal plate made of open cell polyurethane foam impregnated with lubricating oil. The seal plate is mounted on the mobile block under a state in which the seal plate is housed in a casing. The seal plate is configured to move with the mobile block while applying the impregnated lubricating oil to the track rail as the mobile block moves along the track rail, thereby wiping off foreign substances deposited on the track rail. The seal plate is self-lubricating relative to the track rail so that it is possible to smoothly move the mobile block relative to the track rail while improving close contact between the seal plate and the track rail, thereby obtaining high dust-proof effect.
Further, JP 2000-227115 A discloses a dust-proof device in which a plurality of the seal plates are brought into contact with the track rail in an overlapping state, thereby providing higher dust-proof effect.